A. Technical Field
The present invention pertains generally to displays, and relates more particularly to autostereoscopic three-dimensional (3D) displays.
B. Background of the Invention
Three-dimensional movies and television are becoming increasingly more popular. With advances in technology, such as high-definition (HD) television, consumers desire more and better features. According to the “2008 3D Television Report” released in May 2008 by Insight Media, 3D may soon be an add-on feature of high-definition television. Many display manufacturers are developing their own 3D display technologies to meet these market demands.
In the current 3D market, traditional standard two-view stereo remains as the dominant implementation. For example, head mounted displays are widely used in the military training and research community, glass-based projection displays play a key role in the large form 3D display, such as the CAVE® system and PowerWall systems of Mechdyne Corporation, as well as 3D cinemas. However, the requirement of wearing a helmet or glasses limits the use of the 3D technologies. As an alternative solution, autostereoscopic display technologies have attracted increasing attention. Autostereoscopic displays use special light directing devices to create separate viewing windows in the user's space, which allow the user to see 3D images without glasses. Since the designated viewing windows form a viewing space which is significantly larger than the size of the human eye, users can move their heads freely as long as their eyes are within the viewing space.
Current stereoscopic methods used to produce the viewing windows include parallel-barrier-based displays and lenticular-based displays. However, these autostereoscopic display technologies have significant limitation.
For example, parallel-barrier-based displays suffer from several limitations. First, because parallel-barrier displays use light blocking to produce viewing windows, only a small amount of light emitted from each pixel passes through the barrier window. Second, crosstalk between views can be significant. Crosstalk refers to the overlap of viewing areas, which results when one eye sees the image intended for the other eye. When the crosstalk is significant, the brain cannot perceive the stereo effect or cannot perceive it correctly. Third, the use of small apertures in parallel-barrier-based displays can cause diffraction. This problem becomes more acute as the display resolution increases. As the display resolution increases, the barrier aperture size must be decreased, which causes more severe diffraction effects. Fourth, parallel-barrier-based displays typically suffer from limited resolution. For a display with n views, the resolution of the individual view is essentially 1/n of the original display resolution. Because the views have to divide the resolution of the original display, a parallel-barrier-based display's resolution is limited by the original resolution of the display, which is also limited by diffraction as well as the display manufacturer's capability. Fifth, since each view only sees one pixel column out of n associated with one barrier window, there are many dark pixels lines in each view, which creates a “picket fence effect” in the monocular image. Finally, parallel-barrier-based displays typically suffer from having a limited number of viewing windows. In order to generate more viewing windows, the dark slits have to be wider while the slit windows remain unchanged. Obviously, it is impossible to infinitely increase the number of viewing windows without aggregating the artifacts such as reduced brightness and picket fence effect.
Although lenticular-based displays offer some improvements over parallel-barrier-based displays, the use of lenticular sheets also has important drawbacks. Lenticular-based displays offer higher resolution compared with barrier slits; however, it is more difficult and costly to make high quality lenticular sheets than to make simple black-white barriers. In fact, the quality of the display is directly related to the quality of the lenticular sheet used in the display. Aligning a lenticular sheet with a display also requires significant effort. Furthermore, lenticular-based displays also suffer from problems that plague parallel-barrier-based displays, such as crosstalk between view windows, dark line problem, limited resolution, and limited number of viewing windows.